//javascript代码

    $$(".bb").addEvent('change',function(e){

       var order_item_id =  this.get('order_item_id');

       var product_name= this.value;

       new Request.JSON({

            url: "index.php?app=sale&ctl=admin_orders&act=ajax_discount",

            onComplete: function(person, text){

                if(person.status==1){

                    alert(person.msg);

                }else{

                    alert("提交失败");

                }

            }

        }).post('order_item_id='+order_item_id+'&product_name='+product_name);

    });

    //后台方法

    function ajax_discount(){

        $id = $_POST['order_item_id'];

        $product_name =  $_POST['product_name]

        $order_item_mdl = $this->app->model('orders_item');

        $order_item = $order_item_mdl->dump($id);

        $order_item['product_name']=$product_name;

        $order_item_mdl->save($order_item);

        $result = array('status'=>1,'msg'='信息修改成功']);

        echo json_encode($result);

    }